Separate stl into two stl's based on size of chunks-for 3d printing
In edit mode, separate the spheres by loose parts by pressing P >> Loose Parts. Now you have each sphere as a separate object. Put all of these objects in a group by selecting all of them and pressing Ctrl+G.

Now, in Animation Nodes, we will create a loop that only returns one type of sphere based on the vertices count. We first get the vertices count of any of the objects, lets say the first, then we loop over the objects and only return the ones that have a mesh with the same number of vertices as the vertices count we just computed.



Now, hide those objects we just computed using the Object Visibility Output Node.



Select those objects and export them using the Selection Only option, delete those object, unhide the other objects and export them. You now have two files each have only one type of spheres.

Notice that if the two spheres have the same number of vertices but different scales, then, similarly, the volume of the bounding box can be used to filter the objects.